The invention relates to a knot, in particular to a knot for making a net. Usually the weavers knot is used to knot nets, because such a knot can easily be made mechanically.
A knot in two ropes is generally characterised by two pairs of rope ends, each rope having a left and a right end, and an entwining of the ropes linking the ropes to one another. The points at which, in the entwining in each rope, the left end becomes the right end will here and hereinafter be called xe2x80x98turning pointsxe2x80x99. The right and left rope ends are here and hereinafter understood to be the entire lengths of rope after the turning point that ultimately leave the knot on the right and left side, respectively, with any unnecessary crossings that can be avoided without affecting the entwining of the ropes not being considered.
A knot that is frequently used to knot two ropes together is the reef knot. Using the aforementioned definitions, a reef knot can be described as a knot in a first and a second rope with four rope ends, each rope having a left and a right end and the first and the second rope both crossing the ends of the second rope, on one side and the first rope on the other side, respectively, at the turning points, and the left and right ends of the first rope crossing the left and right end, respectively, of the second rope once between the turning points.
Usually the weavers knot is used to knot nets. For plastic fibres commonly used for nets, such as polyamides, polyolefines and polyesters, the weavers knot presents the property that the knot will tighten progressively under stress as a result of these fibres"" relatively high elasticity. This phenomenon is not observed in the case of high-performance (HP) fibres, which are far less elastic. xe2x80x98HP fibresxe2x80x99 are here and hereinafter understood to be fibres with a very high modulus and strength such as high-performance polyethylene (HPPE), polyvinyl alcohol, liquid crystal polymers, aramide and polybisoxazoline (PBO). Because of the great strength of fibres of this type, the fibre may have a smaller cross-section, which in the case of fishing nets presents the advantage that a net made from such fibres will displace less water. Trailing such a net will therefore generate less resistance. This will ensure a substantial saving in fuel.
An important characteristic of fishing nets is that all the meshes of a net have the same dimensions. A regular mesh width can easily be disturbed if a net is retained by an obstacle during use. Especially in the case of nets made from fibres with little elasticity, such as HP fibres, this can lead to slippage in the knots in the net, resulting in meshes of unequal size.
Fishing nets with meshes of unequal size involve the disadvantage that the flow resistance in the water increases. Meshes that are too large will moreover let fish of the desired dimensions pass through, while meshes that are too small will retain fish with dimensions below the minimum dimensions of the allowed size of fish to be caught.
The aim of the invention is to provide a knot with a higher knot slip.
A knot in a first and second rope has been found, with each rope having a left and a right end between which is a turning point, characterised in that, at the turning points, the first and the second rope cross both ends of the second rope, on one side, and of the first rope, on the other side, respectively, the left and right end of each rope forming an intersection after the turning points and the knot between the intersections comprising at least four crossings of the two ropes.
By an xe2x80x98intersectionxe2x80x99 is understood a spot at which the two ends of one rope cross each other.
By a xe2x80x98crossingxe2x80x99 is understood a spot at which the rope ends of different ropes cross each other.
As a result of this the knot slip is more than doubled whereas the strength of the knot does not, or not appreciably, decrease.
It has surprisingly been found that the knot according to the invention results in a substantial improvement of the knot slip also in the case of the materials usually used for nets, such as polyolefines and polyesters. The two ropes cross at least four times. The greater the number of crossings, the greater the knot slip, but the lower the knot strength. In general, the knot according to the invention will comprise not more than eight crossings of the two ropes. A knot with more than eight crossings has insufficient knot strength, contains a too long stretch of rope and is difficult to tie.
Preferably the knot according to the invention comprises four crossings in the two ropes between the intersections. Such a knot is relatively easy to make. Four crossings of the two ropes between the intersections can be formed in different ways. One way of achieving this is that with which one end of the first rope crosses the two ends of the second rope twice. Depending on whether these crossings involve the left or the right end, we will here and hereinafter call the knot according to the invention DIGO(LxL) or DIGO(RxR), which are represented in FIGS. 4 and 5, respectively. The two knots are mirror images of one another. This knot preferably has three intersections.
Another way of obtaining four crossings of the two ropes is based on the circumstance that each end of the first rope crosses the two ends of the second rope once. This can be achieved in two ways, the resulting knots being mirror images of one another. These knots will here and hereinafter be called DIGO(LxR) and DIGO(RxL) and are represented in FIGS. 1 and 2, respectively. This knot preferably has two intersections.
Preferably the four crossings are formed because each end of the first rope crosses the two ends of the second rope once. This will ensure that the knot slip is the same in both ropes.
The invention also relates to a method for making a knot according to the invention.
The method for making the knot in a first and a second rope according to the invention comprises the following steps (FIG. 3):
a) the free-hanging part of the first rope, which is fixed at both ends,
b) is twisted 180xc2x0 to form a loop, with the left rope end, when viewed from above, lying above the right rope end in a crossing with the right rope end;
c) the second rope is inserted through the loop from behind and passed over the crossing;
d) then the second rope is passed under the part of the left first rope end lying above the crossing and is brought forwards and passed to the right in front of the two first rope ends;
e) is passed via the back of the two ends of the first rope and
f) is passed over the left first rope end, under the right first rope end and inserted through the loop from the front.
This method results in a DIGO(RxL) knot.
Another method for making a knot in a first and a second rope according to the invention comprises the following steps:
a) the free-hanging part of the first rope, which is fixed at both ends,
b) is twisted 360xc2x0 to form two crossings, with the right rope end in the bottom crossing, viewed from above, lying in front of the left rope end;
c) the second rope is inserted through the loop from behind and is passed over the part of the right end of the first rope lying above the crossings, after which it is
d) passed to the left under the two first rope ends and,
e) after being passed over itself, viewed from above, the second rope is passed backwards between the left and right ends of the first rope above the two crossings in the first rope,
f) brought forwards between the two crossings in the first rope and
g) inserted through the loop from the front.
This method results in the DIGO(LxL) knot.
The knots made with the aid of the methods described above are novel. The invention therefore also relates to knots obtainable with the methods according to the invention.
Known methods for increasing the knot slip of many knots even further are coating the knot, subjecting the knot to a heat treatment, whether or not under stress, or a combination of these two methods.
The invention also relates to the use of the knot according to the invention in manufacturing a fishing net, in particular in manufacturing a fishing net from predominantly HP fibres. Preferably the knot according to the invention is used in manufacturing a HPPE fishing net.
The invention also relates to a fishing net comprising knots according to the invention. Preferably the fishing net according to the invention consists predominantly of HPPE fibres. In particular in the case of nets of HPPE fibres the triple increase in the knot slip involves the advantage that the meshes"" resistance to deformation is greatly increased.